How are clouds formed?
Water vapor is always present in air. When air is cooled, the water vapor present in the air gets condensed and forms clouds. Air, which is nearer to the surface of the earth, has moisture in the form of water vapor, which is invisible. Cooler air in the higher levels of the atmosphere contains water vapor in its visible form as clouds. In fact, when the temperature is below freezing, clouds are composed of ice crystals and when cloud formation takes place at higher temperatures, clouds contain droplets of water.  Cloud formation is also affected by the movement of air.  All these variable factors account for the different types of clouds that are formed. The size of the water particles that make up clouds can range from 0.0005 to 0.008 cm. 

Different types of clouds
Studies of clouds have yielded more than 100 distinct varieties of clouds.  Clouds are classified into four broad groups – high clouds, middle clouds, low clouds and clouds

Cloud Formation

with vertical development that may extend through all the other three levels. 

The classification of clouds is done on the basis of their appearance and altitude. High clouds are found at levels of eight kilometers or more above the earth. Middle clouds occur at levels ranging from three to six kilometers above the earth’s surface. Low clouds are generally found at an average height of one and half kilometers from the earth’s surface. Clouds that have a vertical formation could range from the height of low clouds i.e., 1.6 kilometers to thirteen kilometers above the earth’s surface. Some clouds form at heights ranging from nineteen to fifty six kilometers above the earth’s surface. Aircrafts flying in high altitudes leave a trail of artificial clouds formed by condensed water vapor from the engine exhaust fumes.  

High clouds are generally wispy in appearance and are referred to as cirrus clouds, cirrus being Latin for hair. Clouds that have a sheet-like appearance are referred to as stratus clouds, the name being derived from the Latin word for layers. Puffy clouds are called cumulus, a word derived from the Latin word for heap. Rain producing clouds are referred to as nimbus, which also traces the origin of its name to a Latin word for rain.  The credit for this system of Latin words goes to English naturalist Luke Howard. 

Can clouds cause problems?
Almost everything has a flipside. Clouds have a very important part to play in our life, but they present their share of problems too. Excess clouds bring down visibility sharply. This hampers the flying of aircrafts. Visibility can be achieved through clouds to a certain extent, with all the navigational instruments that pilots have at their disposal. Still, many a time planes are advised against flying due to low visibility. Vessels sailing in the sea also face navigational problems on cloudy days.